Dark rim on MS lesions seen with standard MRI may mark activity

Possible way of spotting in clinic rim lesions known to drive progression

Marisa Wexler, MS avatar

by Marisa Wexler, MS |

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A researcher uses a flashlight to illuminate a gigantic brain while another scientist looks at it with a magnifying glass.

An imaging feature called the T1-dark rim, which is visible on standard MRI scans of people with multiple sclerosis (MS), could help to identify paramagnetic rim lesions (PRLs), a study suggests.

PRLs are regions of chronic active inflammation that cause ongoing nerve damage. They’re associated with disease activity and are important drivers of disability progression in MS. Traditionally, advanced imaging techniques often beyond clinic use are needed to detect PRLs.

“The T1-dark rim could serve as an alternative marker to identify these lesions, thus potentially enhancing early detection and treatment adjustments for patients with MS at higher risk of disease progression,” the researchers wrote.

This imaging feature was described in the study, “The T1-dark-rim: A novel imaging sign for detecting smoldering inflammation in multiple sclerosis,” published in the European Journal of Radiology.

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MRI scans in clinic can’t detect MS brain lesions of chronic, active inflammation

MS is caused by inflammation in the brain and spinal cord, resulting in areas of tissue damage and inflammation called MS lesions. These lesions are visible on MRI scans, and tracking how they evolve over time and in response to treatment plays a major role in guiding care decisions.

PRLs, also called iron-rim lesions or smoldering lesions, are a specific type of lesion marked by chronic active inflammation. These lesions contain a central core of pronounced myelin loss or demyelination, surrounded by a “rim” of immune cells that are continuously causing nerve damage.

PRLs have been identified as a highly specific marker of MS and studies suggest they may help predict disability worsening.

However, studies of PRLs detected these lesions using an advanced MRI protocol called susceptibility-weighted imaging or SWI. Although SWI has worked well in a research setting, it isn’t routinely done in MS clinical care, which has been a major obstacle toward the use of PRLs as a diagnostic and prognostic tool.

A recent study reported that, on standard MRI scans, PRLs frequently show a dark “rim” around the lesion itself, which is not observed with other lesions. Building on that observation, researchers in Spain tested whether this so-called “T1-dark rim” could be used to identify PRLs without the need for SWI.

They analyzed brain images from 63 people with MS. Each of the patients had two images taken: one using SWI, and another using a protocol called 3D T1 turbo field echo (3DT1TFE), which is routinely done in MS clinical care.

T1-dark rims seen on standard MRI show potential to spot smoldering lesions

Experts analyzed each of the images separately, identifying PRLs in the images from SWI and T1-dark rims in the 3DT1TFE images. Then, they looked at the degree of overlap between these two techniques.

Results showed that 60 true PRLs were identified by SWI, and all but two of the PRLs (58 out of 60) also were detected as T1-dark rims on 3DT1TFE, suggesting the T1-dark rim may be a useful surrogate for PRL detection.

“Our study introduces the T1-dark rim sign as a highly sensitive and accessible imaging marker for the detection of iron-rim lesions,” the scientists concluded. “As SWI is not part of standard clinical MS imaging protocols, the T1-dark rim could serve as an alternative marker to identify these lesions, thus potentially enhancing early detection and treatment adjustments for patients with MS at higher risk of disease progression.”

The other 20 lesions were identified as T1-dark rims on 3DT1TFE but were not marked as PRLs by SWI. Reasons for this relatively high false-positive rate are not clear, and the researchers called for further studies to examine the clinical significance of T1-dark rim lesions that aren’t PRLs.

Scientists also noted that this study is limited by its small sample size and reliance on just a few experts to interpret images, so further work is needed to validate these results.